There is no limit to the number of items you can carry; however, the Spear, Axe, and Blood Dagger all say "you cannot use another weapon while you're using this one," or something to that effect, which prevents you from adding all the bonuses to one attack.

Then the Revolver is only for Speed attacks, the Ring for Sanity attacks, and the Dynamite is "instead of making an attack," so none of those stack with each other or with the aforementioned weapons.

Also, as per the errata, you can't use an item and then trade/drop it in the same turn...so, for example, you can't pass the Spear around in a circle and let everyone attack with it in one round.